Ocean Waves & Tsunamis

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Waves travel on the surface of sea water as ripples or ups and downs. The ups of a wave are called crests and downs are called troughs. Waves are produced due to movement of water molecules.

They possess kinetic energy (due to motion).Usually it is not water which is moving horizontally because most of water is not being moved along but it is energy in water waves which is moving. The energy of waves is sometimes extremely large.

For example:

A single wave can exert a hammer blow of up to 500 tons on each square meter of a wall and hurl stones and boulders up to many meters inland. The greatest amount of wave energy in ocean waters is derived from small wind generated waves. Moist waves are caused by wind blowing over the water. A small breeze can create ripple of high energy and speed because of greater surface area. Height of the waves can range from mere ripples to about 50 feet (the highest recorded was 112 feet).

The height of the waves increases with the speed of the wind, the length of time it has been blowing, and the distance the wind has traveled over the ocean. The wind speed in metric km is about twice the wave height in meters.

Note: Knot is a unit for speed of wind over sea or a ship. 1 knot 1.166 miles per hour or 1.876 kilometers per hour.

Tsunamis:

The most destructive waves in the ocean are tsunamis, often wrongly called tidal waves. They are not caused by tides, but by underwater earthquakes, landslides, volcanic eruption, or by hurricanes. These disturbances cause the sea bed to move very quickly, which shifts a large amount of water and disrupts the sea surface. A train of waves travels away from the source of disturbance. Tsunamis travel extremely fast — up to 500 miles per hour (805 kilometers per hour).

They have a long wavelength (distance from one crest to the next, or one trough to the next), their crests often being 93 miles (150 kilometers apart). In the open ocean they are very low and usually pass ships unnoticed and in shallow waters it’s very high. Tsunamis can cause devastation on sea shore. The eruption of a volcano in 1883 on the island of Krakatoa caused destructive tsunamis. Waves 130 feet (40 meters) high crashed into the nearby islands and even swept a boat far inland. The shores of Pacific witness Tsunamis more than any other oceans in the world. It is because volcanic eruptions and earthquakes occur frequently in the Pacific Ocean.